1. Field of the Invention
The present invention relates to a method of manufacturing a laminated steel sheet and an apparatus for carrying out such a method, and more particularly to a method of manufacturing a laminated steel sheet which is capable of increasing the adhesive strength between a base steel sheet and lamination sheets attached to the surfaces of the base steel sheet, and of utilizing various kinds of steel for the base steel sheet, and an apparatus for carrying out such a method.
2. Description of the Related Art
As well known to those skilled in the art, various kinds or shapes of steel sheets are manufactured and distributed according to the purpose of their uses. Such steel sheets may be subjected to a plating process or a chemical treatment, by which the steel sheets have various properties. Recently, a laminated steel sheet comprising a base steel sheet and lamination sheets made of various materials, the lamination sheets being attached to the surfaces of the base steel sheet, has been manufactured and widely used to improve corrosion resistance, abrasion resistance, impact resistance, chemical resistance, durability, etc. of the sheet.
Such a laminated steel sheet may be manufactured by shot blasting a galvanized steel sheet and high frequency laminating the shot blasted galvanized steel sheet with polyethylene sheets. This laminated steel sheet may be used, for example, for a corrugated pipe or other structural members disposed in the ground or on the ground, through which rainwater or sewage flows.
However, the aforesaid laminated steel sheet is not of a high quality in that adhesive strength is poor between the base steel sheet and the lamination sheets.
The conventional method for manufacturing laminated steel sheets is mainly applied to the expensive galvanized steel sheets, not to general steel sheets.
Furthermore, the conventional method for manufacturing laminated steel sheets utilizes the high-frequency laminating system, which is mainly applied to a very thin steel sheet. Consequently, a new method utilizing a low-frequency laminating system as well as a high-frequency laminating system is needed.